/* vim: set expandtab tabstop=4 softtabstop=4 shiftwidth=4: */
/*
 * Copyright © 2016 Intel Corporation
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice (including the next
 * paragraph) shall be included in all copies or substantial portions of the
 * Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
 * IN THE SOFTWARE.
 */

#define _GNU_SOURCE
#include <dlfcn.h>
#include <link.h>
#include <stddef.h>
#include <string.h>

#include "build-id.h"

#ifndef NT_GNU_BUILD_ID
#define NT_GNU_BUILD_ID 3
#endif

#ifndef ElfW
#define ElfW(type) Elf_##type
#endif

#define ALIGN(val, align)       (((val) + (align) - 1) & ~((align) - 1))

struct build_id_note {
    ElfW(Nhdr) nhdr;

    char name[4];
    uint8_t build_id[0];
};

enum tag { BY_NAME, BY_SYMBOL };

struct callback_data {
    union {
        const char *name;

        /* Base address of shared object, taken from Dl_info::dli_fbase */
        const void *dli_fbase;
    };
    enum tag tag;
    struct build_id_note *note;
};

static int
build_id_find_nhdr_callback(struct dl_phdr_info *info, size_t size, void *data_)
{
    struct callback_data *data = data_;

    if (data->tag == BY_NAME)
        if (!info->dlpi_name || strcmp(info->dlpi_name, data->name) != 0)
            return 0;

    if (data->tag == BY_SYMBOL) {
       /* Calculate address where shared object is mapped into the process space.
        * (Using the base address and the virtual address of the first LOAD segment)
        */
       void *map_start = NULL;
       for (unsigned i = 0; i < info->dlpi_phnum; i++) {
          if (info->dlpi_phdr[i].p_type == PT_LOAD) {
             map_start = (void *)(info->dlpi_addr + info->dlpi_phdr[i].p_vaddr);
             break;
          }
       }

       if (map_start != data->dli_fbase)
          return 0;
    }

    for (unsigned i = 0; i < info->dlpi_phnum; i++) {
        if (info->dlpi_phdr[i].p_type != PT_NOTE)
            continue;

        struct build_id_note *note = (void *)(info->dlpi_addr +
                                              info->dlpi_phdr[i].p_vaddr);
        ptrdiff_t len = info->dlpi_phdr[i].p_filesz;

        while (len >= sizeof(struct build_id_note)) {
            if (note->nhdr.n_type == NT_GNU_BUILD_ID &&
                note->nhdr.n_descsz != 0 &&
                note->nhdr.n_namesz == 4 &&
                memcmp(note->name, "GNU", 4) == 0) {
                data->note = note;
                return 1;
            }

            size_t offset = sizeof(ElfW(Nhdr)) +
                            ALIGN(note->nhdr.n_namesz, 4) +
                            ALIGN(note->nhdr.n_descsz, 4);
            note = (struct build_id_note *)((char *)note + offset);
            len -= offset;
        }
    }

    return 0;
}

const struct build_id_note *
build_id_find_nhdr_by_name(const char *name)
{
    struct callback_data data = {
        .tag = BY_NAME,
        .name = name,
        .note = NULL,
    };

    if (!dl_iterate_phdr(build_id_find_nhdr_callback, &data))
        return NULL;

    return data.note;
}

const struct build_id_note *
build_id_find_nhdr_by_symbol(const void *symbol)
{
    Dl_info info;

    if (!dladdr(symbol, &info))
        return NULL;

    if (!info.dli_fbase)
        return NULL;

    struct callback_data data = {
        .tag = BY_SYMBOL,
        .dli_fbase = info.dli_fbase,
        .note = NULL,
    };

    if (!dl_iterate_phdr(build_id_find_nhdr_callback, &data))
        return NULL;

    return data.note;
}

ElfW(Word)
build_id_length(const struct build_id_note *note)
{
    return note->nhdr.n_descsz;
}

const uint8_t *
build_id_data(const struct build_id_note *note)
{
    return note->build_id;
}
